Roll of flexible glass and method for rolling

ABSTRACT

A roll ( 10 ) of glass ribbon ( 20 ), having a thickness of 0.3 mm or less, wherein a thickness compliant material interlayer ( 40 ) is wound together with the glass ribbon. The characteristics of the interlayer are chosen to form the roll with minimal lateral offset ( 9 ). For example, the static coefficient of friction between the interlayer and the glass ribbon may be greater than or equal to 3.0 (as measured with a vertical force of 0.5 N). Other characteristics may include the width, thickness, and compliance, of the interlayer. There is also disclosed a method of rolling a glass ribbon wherein the roll winding parameters, for example web tension and pressure between the layers of the roll, are chosen to minimize the lateral offset.

This application claims the priority of U.S. Provisional ApplicationSer. No. 61/349,438 filed on May 28, 2010.

FIELD OF INVENTION

The invention is directed to a roll of flexible glass and a method forrolling the glass. More particularly, the invention is directed to aroll of flexible glass ribbon wound together with an interlayer, and toa method for rolling them together.

TECHNICAL BACKGROUND

Although formed as a continuous ribbon, glass is typically segmentedinto sheets as soon as it has cooled and solidified. Recent producttrends—in ePaper front plane substrates, protective cover sheets inphotovoltaic modules, touch sensors, solid state lighting, andelectronics, for example—have resulted in requirements for thinner andthinner glass. As glass thicknesses continues to decrease, however,these sheets become more flexible. This creates a challenge from ahandling perspective, particularly for glass of 0.3 mm or thinner.Accordingly, there have been attempts to roll thin glass as a manner offacilitating handling. However, there are several unique features ofglass that create challenges for successfully implementing a rollingprocess. First the edge “beads” of the glass, as formed, aresubstantially thicker than the constant thickness area in between.Second glass is extremely sensitive to surface defects. These defectscreate stress points that generate cracks and lead to breakage. Thus itis not advisable to have direct surface to surface contact of glass toitself, as is typical in a spooled roll of material. The challenges fromthese first two characteristics have been addressed by using variousinterleaf materials between layers of the glass ribbon when winding.Third, as noticed by the inventors of the present disclosure, and whichhas gone unaddressed—in terms of their effect on rolling thin glassribbon, i.e. 0.3 mm or thinner—to this point as far as the presentinventors are aware, is that the forming process can introducedifferential thickness across the width of the glass ribbon and/orcamber (continuous curvature in one direction caused by differentialcooling between the two edge beads). When rolling a glass ribbon withdifferential cross-ribbon thickness and/or camber, lateral forces aregenerated in the spooled roll that result in angled, rather thanstraight, side walls on the wound roll. In some cases, the angle of theside wall may lead to the glass ribbon contacting a flange of a spoolonto which the glass ribbon is being wound, thereby risking damage tothe glass ribbon. Additionally, the angled side wall of the spool leadsto difficulties in processing, when unwinding the roll to use the glassribbon in a continuous manufacturing process. Accordingly, there is aneed for rolls of wound glass ribbon having straighter side walls.

SUMMARY

In order to form a roll of wound glass ribbon having straight sidewalls, the inventors have found that the effects of the differentialcross-ribbon thickness and/or camber, among other things, can becounteracted by appropriately choosing an interleaf material and rollingconditions.

Some pertinent characteristics of the interleaf material are itscoefficient of friction with the glass ribbon being wound, the width ofthe interlayer with respect to the glass ribbon, compliance, andthickness. First, choosing an interleaf material with a sufficientcoefficient of friction between it and the glass ribbon being woundassists in providing a force to resist that produced by the differentialthickness and/or camber. Additionally, a sufficient coefficient offriction assists in maintaining roll integrity during subsequenthandling, even in rolls that have very low pressure between the layersin the roll, as discussed below. More specifically, a beneficial staticcoefficient of friction between the interlayer and the glass ribbon wasfound to be greater than or equal to about 3.0 (as measured with avertical force of 0.5N), another was found to be from about 3.0 to about4.6 (as measured with a vertical force of 0.5 N), and another was foundto be from about 3.4 to about 4.2 (as measured with a vertical force of0.5N). Second, an interlayer having a width less than that of the glassribbon allows the contact between the interlayer and the glass ribbon tooccur in the central area of the glass ribbon wherein there is lowthickness variation. Additionally, these relative widths allow the glassribbon some freedom to pivot about its longitudinal axis, which mayresult from the effects of camber in the glass ribbon. Third, theinterlayer should be thickness compliant, or have some give to it whencompressed, in order to absorb any thickness differences that may bepresent in the central portion of the glass ribbon. A suitable stiffnessfor the interlayer material was found to be less than or equal to about28.14 N/mm, or less than or equal to about 27.12 N/mm, or less than orequal to about 26.1 N/mm, wherein the lower bound for all ranges wasgreater than zero. In order to achieve the above-noted stiffness, theinterlayer may be formed from, for example, a polyethylene foam (eitheropen or closed cell), a corrugated paper material, or a sheet of softpolyvinyl material having an embossed or textured surface. Fourth, whenwinding a glass ribbon having beads on its edges, the interlayer ischosen to have a sufficient thickness, when compressed under the rollingconditions as discussed below, so that the beads do not touch oneanother. The ability to roll the glass ribbon with its beads onfacilitates manufacture of the glass ribbon.

Some pertinent rolling conditions are web tension and pressure betweenthe layers in the roll. More specifically, the inventors found thattypical web winding process parameters of 1-2 pounds per linear inch(0.179 to 0.357 kg/cm) of web tension, and 15-50 pounds per square inch(1.054 to 3.515 kg/square cm) of pressure between the layers, when usedwith a thin glass ribbon produced angled side walls in the roll.Further, contrary to conventional wisdom, the inventors found thatincreasing the web tension and pressure between the layers actually madethe side wall characteristics worse. Surprisingly, the inventors foundthat using lower web tension and lower pressure between the layersproduced straighter side walls in the roll. More particularly, a webtension of greater than 0 pounds per linear inch (0 kg/cm), but 0.25pounds per linear inch (0.45 kg/cm) or less, produced straight sidewalls on the roll. Additionally, a pressure between the layers in theroll of 10 pounds per square inch (0.703 kg/square cm) or less, butgreater than 0 pounds per square inch (0 kg/square cm), producedstraight side walls on the roll. Another pressure between the layers inthe roll of 7 pounds per square inch (0.492 kg/square cm) or less, butgreater than 0 pounds per square inch (0 kg/square cm), also producedstraight side walls on the roll. Further, the above-noted coefficientsof friction between the interlayer and glass ribbon facilitated usingthe above-noted unusually low web tension and pressure between thelayers in the roll. Also, if there is not sufficient interlayer frictiondue to a combination of too low a pressure between the layers and/or toolow a coefficient of friction, the successive wraps can slide laterallyon each other, undesirably creating a “telescoped” side wall.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from the description or recognized by practicing theinvention as exemplified in the written description and the appendeddrawings. It is to be understood that both the foregoing generaldescription and the following detailed description are merely exemplaryof the invention, and are intended to provide an overview or frameworkto understanding the nature and character of the invention as it isclaimed.

The accompanying drawings are included to provide a furtherunderstanding of principles of the invention, and are incorporated inand constitute a part of this specification. The drawings illustrate oneor more embodiment(s), and together with the description serve toexplain, by way of example, principles and operation of the invention.It is to be understood that various features of the invention disclosedin this specification and in the drawings can be used in any and allcombinations. By way of non-limiting example the various features of theinvention may be combined with one another as set forth in the followingaspects:

According to a first aspect, there is provided a roll of glass ribbon,comprising:

-   -   a glass ribbon;    -   an interlayer wound together with the glass ribbon, wherein the        glass ribbon has a thickness of 0.3 mm or less,    -   wherein the static coefficient of friction between the        interlayer and the glass ribbon is greater than or equal to 3.0        (as measured with a vertical force of 0.5 N).

According to a second aspect, there is provided the roll according toAspect 1 or aspect 31, wherein the static coefficient of friction isfrom 3.0 to 4.6 (as measured with a vertical force of 0.5 N).

According to a third aspect, there is provided the roll according toAspect 1 or aspect 31, wherein the static coefficient of friction isfrom 3.4 to 4.2 (as measured with a vertical force of 0.5 N).

According to a fourth aspect, there is provided the roll according toany one of Aspects 1-3 or 31-36, wherein the stiffness of the interlayeris less than or equal to 28.14 N/mm.

According to a fifth aspect, there is provided the roll according to anyone of Aspects 1-3 or 31-36, wherein the stiffness of the interlayer isless than or equal to 27.12 N/mm.

According to a sixth aspect, there is provided the roll according to anyone of Aspects 1-3 or 31, wherein the stiffness of the interlayer isless than or equal to 26.1 N/mm.

According to a seventh aspect, there is provided the roll according toany one of Aspects 1-6, wherein the pressure between successive layersof glass ribbon is less than or equal to 10 pounds per square inch(0.703 kg/square cm).

According to an eighth aspect, there is provided the roll according toany one of Aspects 1-7 or 31-36, wherein the interlayer and glass ribbonare wound so that a lateral offset between an inner-most layer of theglass ribbon and an outer-most layer of glass ribbon is less than orequal to 1.6 mm, even when the roll includes up to 150 or more layers ofglass ribbon.

According to a ninth aspect, there is provided the roll according to anyone of Aspects 1-8 or 31-36, wherein the interlayer comprises a firstportion and a second portion disposed at a distance from one another andhaving a width, wherein the width is centered within ±10% of the centerof the glass ribbon,

-   -   wherein the glass ribbon has an outboard end portion, and    -   further wherein there is no interlayer disposed on the outboard        end portion.

According to a tenth aspect, there is provided the roll according to anyone of Aspects 1-8 or 31-36, wherein the interlayer has a first width,the glass ribbon has a second width and an outboard end portion,

-   -   wherein the first width is less than the second width, and    -   further wherein there is no interlayer disposed on the outboard        end portion.

According to an eleventh aspect, there is provided the roll according toany one of Aspects 1-10 or 31-36, wherein the glass ribbon comprises abead on one of its edges.

According to a twelfth aspect, there is provided the roll according toAspect 11, wherein the interlayer has a thickness when compressed at aroll-winding pressure up to 70 kPa (10 psi), the bead has a thickness,and the interlayer thickness is greater than a difference between thebead thickness and the ribbon thickness.

According to a thirteenth aspect, there is provided the roll accordingto any one of Aspects 1-12, wherein the interlayer comprisespolyethylene foam.

According to a fourteenth aspect, there is provided the roll accordingto any one of Aspects 1-13, further comprising a core around which theglass ribbon and the interlayer are wound.

According to a fifteenth aspect, there is provided a method of winding aglass ribbon, comprising:

-   -   winding an interlayer together with a glass ribbon, wherein the        glass ribbon has a thickness of 0.3 mm or less,    -   wherein the static coefficient of friction between the        interlayer and the glass ribbon is greater than or equal to 3.0        (as measured with a vertical force of 0.5 N).

According to a sixteenth aspect, there is provided the method accordingto Aspect 15, wherein the static coefficient of friction is from 3.0 to4.6 (as measured with a vertical force of 0.5 N).

According to a seventeenth aspect, there is provided the methodaccording to Aspect 15, wherein the static coefficient of friction isfrom 3.4 to 4.2 (as measured with a vertical force of 0.5 N).

According to an eighteenth aspect, there is provided the methodaccording to any one of Aspects 15-17, wherein the stiffness of theinterlayer is less than or equal to 28.14 N/mm.

According to a nineteenth aspect, there is provided the method accordingto any one of Aspects 15-17, wherein the stiffness of the interlayer isless than or equal to 27.12 N/mm.

According to a twentieth aspect, there is provided the method accordingto any one of Aspects 15-17, wherein the stiffness of the interlayer isless than or equal to 26.1 N/mm.

According to a twenty first aspect, there is provided the methodaccording to any one of Aspects 15-20, wherein the winding is performedso that a resulting pressure between successive layers of glass ribbonis greater than zero pounds per square inch (0 kg/square cm) and is lessthan or equal to 10 pounds per square inch (0.703 kg/square cm).

According to a twenty second aspect, there is provided the method aaccording to any one of Aspects 15-21, wherein the winding is performedto that a resulting pressure between successive layers of glass ribbonis greater than zero pounds per square inch (0 kg/square cm) and is lessthan or equal to 7 pounds per square inch (0.492 kg/square cm).

According to a twenty third aspect, there is provided the methodaccording to any one of Aspects 15-22, wherein the winding is performedwith a web tension of greater than zero pounds per linear inch (0 kg/cm)and of less than or equal to 0.25 pounds per linear inch (0.045 kg/cm)on the glass ribbon.

According to a twenty fourth aspect, there is provided the methodaccording to any one of Aspects 15-23, wherein the winding is performedso that the glass ribbon is disposed in an inner-most layer and anouter-most layer, wherein a lateral offset between the inner-most layerand the outer-most layer is less than or equal to 1.6 mm, evening rollshaving up to about 150 layers or more of glass ribbon 20, for example,more than 2 layers, more than 3 layers, more than 4 layers, more than 5layers, more than 6 layers, more than 7 layers, more than 8 layers, morethan 9 layers, more than 10 layers, more than 15 layers, more than 20layers, more than 30 layers, more than 40 layers, more than 50 layers,more than 60 layers, more than 70 layers, more than 80 layers, more than90 layers, more than 100 layers, more than 110 layers, more than 120layers, more than 130 layers, more than 140 layers, from 1-150 layers,from 2-150 layers, from 3-150 layers, from 4-150 layers, from 5-150layers, from 6-150 layers, from 7-150 layers, from 8-150 layers, from9-150 layers, from 10-150 layers, from 15-150 layers, from 20-150layers, from 30-150 layers, from 40-150 layers, from 50-150 layers, from60-150 layers, from 70-150 layers, from 80-150 layers, from 90-150layers, from 100-150 layers, from 110-150 layers, from 120-150 layers,from 130-150 layers, or from 140-150 layers.

According to a twenty fifth aspect, there is provided the methodaccording to any one of Aspects 15-24, wherein the interlayer comprisesa first portion and a second portion disposed at a distance from oneanother and having a width, wherein the width is centered within ±10% ofthe center of the glass ribbon,

-   -   wherein the glass ribbon has an outboard end portion, and    -   further wherein there is no interlayer disposed on the outboard        end portion.

According to a twenty sixth aspect, there is provided the methodaccording to any one of Aspects 15-24, wherein the interlayer has afirst width, the glass ribbon has a second width and an outboard endportion,

-   -   wherein the first width is less than the second width, and    -   further wherein there is no interlayer disposed on the outboard        end portion.

According to a twenty seventh aspect, there is provided the methodaccording to any one of Aspects 15-26, wherein the glass ribboncomprises a bead on one of its edges.

According to a twenty eighth aspect, there is provided the methodaccording to Aspect 27, wherein the interlayer has a thickness whencompressed at a roll-winding pressure up to 70 kPa (10 psi), the beadhas a thickness, and the interlayer thickness is greater than adifference between the bead thickness and the ribbon thickness.

According to a twenty ninth aspect, there is provided the methodaccording to any one of Aspects 15-28, wherein the interlayer comprisespolyethylene foam.

According to a thirtieth aspect, there is provided the method accordingto any one of Aspects 15-29, wherein the winding comprises winding theglass ribbon and interlayer around a core.

According to a thirty first aspect, there is provided a roll of materialcomprising: interleaving material wound together with glass ribbon,wherein a pressure between layers in the roll is ≦10 pounds per squareinch (0.703 kg/square cm), and is greater than 0 pounds per square inch(0 kg/square cm).

According to a thirty second aspect, there is provided the roll ofmaterial of aspect 31, wherein the pressure between layers in the rollis ≦7 pounds per square inch (0.492 kg/square cm), and is greater than 0pounds per square inch (0 kg/square cm).

According to a thirty third aspect, there is provided the roll ofmaterial of any one of aspect 31 or aspect 32, wherein the interleavingmaterial is thickness compliant.

According to a thirty fourth aspect, there is provided the roll ofmaterial of aspect 33, wherein the interleaving material is polyethylenefoam.

According to a thirty fifth aspect, there is provided the roll ofmaterial of any one of aspects 31-34, wherein the inter-layer rollpressure is approximately constant throughout the roll.

According to a thirty sixth aspect, there is provided the roll ofmaterial of any one of aspects 31-35, wherein the glass ribbon has athickness ≦0.3 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a roll winding process.

FIG. 2 is a schematic cross-section of a roll of glass ribbon andinterlayer material as taken along line 2-2 in FIG. 1.

FIG. 3 is a schematic top view of the roll in FIG. 1.

FIG. 4 is schematic cross-section of a roll of glass ribbon andinterlayer similar to that shown in FIG. 2.

FIG. 5 is a schematic cross-section of a roll of glass ribbon andinterlayer material, similar to that shown in FIG. 2, but according toanother embodiment.

FIG. 6 is a schematic cross-section of a roll of glass ribbon andinterlayer material, similar to that shown in FIG. 2, but according toanother embodiment.

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation andnot limitation, example embodiments disclosing specific details are setforth to provide a thorough understanding of various principles of thepresent invention. However, it will be apparent to one having ordinaryskill in the art, having had the benefit of the present disclosure, thatthe present invention may be practiced in other embodiments that departfrom the specific details disclosed herein. Moreover, descriptions ofwell-known devices, methods and materials may be omitted so as not toobscure the description of various principles of the present invention.Finally, wherever applicable, like reference numerals refer to likeelements.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another embodiment. Itwill be further understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

Directional terms as used herein—for example up, down, right, left,front, back, top, bottom—are made only with reference to the figures asdrawn and are not intended to imply absolute orientation.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order. Accordingly, where a method claim doesnot actually recite an order to be followed by its steps or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is no way intended thatan order be inferred, in any respect. This holds for any possiblenon-express basis for interpretation, including: matters of logic withrespect to arrangement of steps or operational flow; plain meaningderived from grammatical organization or punctuation; the number or typeof embodiments described in the specification.

As used herein, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to a “component” includes aspects having two or moresuch components, unless the context clearly indicates otherwise.

FIG. 1 is a schematic drawing of a process for rolling a glass ribbon20. The glass ribbon 20 is—after being produced by any suitable method,for example, down-draw, fusion draw, up-draw, slot draw, or float—fedalong direction 1 toward roll 10, which rotates in a direction 11. Atthe same time, an interlayer material 40 is unwound from roll 2 rotatingin direction 3 and is fed along direction 4. The interlayer 40 ispositioned relative to the roll 10 by guide rollers 16. According to oneaspect, the interlayer 40 is wound around a core 12 (see FIG. 2) one ormore times before glass ribbon 20 is fed into the nip 6 betweensuccessive layers of interlayer 40. According to another aspect, theglass ribbon 20 is wound around the core 12 and the interlayer 40 isthen fed into a nip between successive layers of glass ribbon 20,although the former aspect is preferred. In either case, the glassribbon 20 and interlayer 40 are wound together to form a roll 10 aroundcore 12. The core 12 may remain in the roll 10 or be removed therefrom.When the core 12 is to remain in the roll 10, the inner-most layer(either interlayer material or glass ribbon) may be attached to the core12. Keeping the core 12 in the roll 10, and attaching the interlayermaterial 40 to the core 12 assists in preventing the entire spooledglass/interlayer pack from side shifting during unwinding in subsequentprocesses steps.

A cross section of the roll 10 is shown in FIG. 2, which is a view takenalong line 2-2 in FIG. 1, but which omits the top interlayer so as tomake illustration more clear. As seen in FIG. 2, the roll 10 includesglass ribbon 20, interlayer 40, and optionally a core 12 around whichthe glass ribbon 20 and interlayer 40 are wound. The core 12, whenpresent, includes a central longitudinal axis 13, and a central axis 14in the width-wise direction of the core 12.

The glass ribbon 20 is disposed in an inner-most layer 21, anintermediate layer 23, and an outermost layer 25. Although only threelayers are shown, there may be any suitable number (including zero) ofintermediate layers 23 between layers 21 and 25. The glass ribbon 20 hasa thickness 26, which may be from about 50 microns to about 300 microns,and a width 24. The glass ribbon 20 also includes outboard end portions28 in which there is the greatest likelihood of thickness variation dueto the forming process. Further, the glass ribbon includes edges 204which may be as-formed edges or cut edges. Still further, there is alateral offset 9 between the inner-most layer 21 and the outer-mostlayer 25 of the glass ribbon. A lateral offset 9 may also exist betweenany two adjacent layers of the glass ribbon 20. Moreover, as shown inFIG. 3, the glass ribbon 20 includes a central longitudinal axis 22.

As shown in FIG. 2, according to one aspect, the interlayer material 40is formed as a first strip 41 and a second strip 43 separated by adistance 45. The interlayer 40 includes an overall width 42 betweenoutside edges 44 on the strips 41, 43 in one layer. Also, the interlayer40 includes a thickness 46.

The effects of camber (continuous curvature in one direction caused bydifferential cooling between the two edge beads during the formingprocess, for example) will be explained with reference to FIG. 3, whichis a top view of the roll 10 (without interlayer 40 for purposes offacilitating explanation). For simplicity in this discussion, it isassumed that camber is the only factor affecting the lateral offset ofthe roll 10. As core 12 is rotated about central longitudinal axis 13,glass ribbon 20 is wound into roll 10. If there were no camber in theglass ribbon 20, the central longitudinal axis 22 of the glass ribbon 20would remain substantially perpendicular to the central longitudinalaxis 13, whereby the glass ribbon 20 would be wound into roll 10 havingstraight side walls, i.e., there would be little if any lateral offset.However, in the presence of camber, the glass ribbon 20 is continuouslycurved so that the longitudinal axis 22 is bent in the direction shownin an exaggerated manner by double headed arrow 15, thereby producingforces on the glass ribbon 20 making it tend to shift in the directionof arrow 5, whereby the sides of roll 10 become angled, and the lateraloffset may increase.

In order to form a roll 10 of wound glass ribbon having straight sidewalls, i.e., one with a small lateral offset 9 (from layer to adjacentlayer of the glass ribbon, as well as overall from inner-most layer 21to outer-most layer 25 of glass ribbon), the inventors have found thatthe effects of camber, among other things, can be counteracted byappropriately choosing an interleaf material and rolling conditions.

Some pertinent characteristics of the interleaf material are itscoefficient of friction with the glass ribbon being wound, the width ofthe interlayer with respect to that of the glass ribbon, compliance, andthickness.

The inventors have found that choosing an interlayer with a staticcoefficient of friction of greater than or equal to about 3.0 (asmeasured with a vertical force of 0.5N), or from about 3.0 to about 4.6(as measured with a vertical force of 0.5 N), or from about 3.4 to about4.2 (as measured with a vertical force of 0.5N) with the glass ribbonassists in maintaining a roll with straight side walls. A staticcoefficient of friction in this range assists in producing forces thatresist the effects of camber as described above in connection with FIG.2, and that assist in holding the layers of the roll in place duringhandling. The higher the static coefficient of friction, the moreresistant to the effects of camber the roll will be, and the more stableduring handling the roll will be. If the static coefficient of frictionbecomes too small, then there are not produced sufficient forces toresist the effects of camber in the glass ribbon as it is wound and thewalls of the roll become angled, stepped, or otherwise no longerstraight. Further, if the static coefficient of friction is too low,there are not sufficient forces to hold the layers of the roll in placeduring handling of the roll.

By choosing an interlayer material 40 having a static coefficient offriction within the above-noted ranges, there can be produced a rollhaving a lateral offset 9 (see FIG. 2) between an inner-most layer 21 ofthe glass ribbon 20 and an outer-most layer 25 of the glass ribbon ofless than or equal to 1.6 mm. A lateral offset 9 of less than or equalto 1.6 mm can be obtained even in rolls 10 having up to about 150 layersor more of glass ribbon 20, for example, more than 2 layers, more than 3layers, more than 4 layers, more than 5 layers, more than 6 layers, morethan 7 layers, more than 8 layers, more than 9 layers, more than 10layers, more than 15 layers, more than 20 layers, more than 30 layers,more than 40 layers, more than 50 layers, more than 60 layers, more than70 layers, more than 80 layers, more than 90 layers, more than 100layers, more than 110 layers, more than 120 layers, more than 130layers, more than 140 layers, from 1-150 layers, from 2-150 layers, from3-150 layers, from 4-150 layers, from 5-150 layers, from 6-150 layers,from 7-150 layers, from 8-150 layers, from 9-150 layers, from 10-150layers, from 15-150 layers, from 20-150 layers, from 30-150 layers, from40-150 layers, from 50-150 layers, from 60-150 layers, from 70-150layers, from 80-150 layers, from 90-150 layers, from 100-150 layers,from 110-150 layers, from 120-150 layers, from 130-150 layers, or from140-150 layers. This small amount of lateral offset 9 makes the rolleasy to unwind into a manufacturing process.

Width and thickness of the interlayer material 40 also assist inproducing a roll 10 with straight side walls. For example, withreference to FIG. 2, the width 42 of the interlayer 40 may be chosen toas to be less than the width 24 of the glass ribbon. By choosing thewidth 42 to be less than the width 24, the glass ribbon 20 has morefreedom to pivot in the direction of double-headed arrow 8 due to theeffects of differential cross web thickness and/or camber therebyreducing the amount of compression required to compensate for theseeffects. Additionally, the interlayer 40 is placed away from theoutboard portions 28 of the glass ribbon 20. Accordingly, by placing theinterlayer material 41, 43 on the central portion of the glass ribbon 20in which there is less likelihood of thickness variation, the roll 10becomes more stable and more likely to have straight side walls.Further, the strips 41, 43 may be placed so that the distance 45 iscentered within ±10% from the center 7 (in the width-wise direction) ofthe glass ribbon 20. See FIG. 4. Alternatively, or in addition thereto,the strips may be placed so that the overall width 42 is centered within±10% from the center 7 of the glass ribbon 20. See FIG. 2. In thislatter case, again the strips are placed away from the outboard portions28. The latter case may be used with either two strips 41, 43, or whenmore or less than two strips are present.

FIG. 5 shows alternative embodiments of each the glass ribbon 20 and theinterlayer 40. It is to be understood that the glass ribbon 20 shown inthis figure may be used with the interlayer material of the otherfigures, and the interlayer 40 in this figure may be used with the glassribbon 20 of the other figures. The main differences from the otherfigures lie in the physical configuration of the glass ribbon 20 andinterlayer material 40. Accordingly, for ease in description mainly thedifferences will be described with the understanding that the remainingproperties, and like characteristics as denoted by like referencenumerals, may remain the same. In this figure the glass ribbon 20 isshown as including beads 30 having a thickness 32. Further, theinterlayer material 40 is formed as one continuous piece having a width42, outside edges 44, and a thickness 46. The thickness 46 is chosen sothat when the interlayer 40 is subject to a pressure between the layersin the roll, as described below, the interlayer 40 maintains a gap 34between adjacent beads 30, thereby allowing the glass ribbon 20 to bewound into roll 10 without damage from the beads 30 contacting oneanother. Again, as noted above, the width 42 is less than the width 24,and the interlayer material 40 is not disposed on the outboard endportions 28 wherein the thickness variation in the glass ribbon isexaggerated due to the presence of the beads 30. Again, the width 42 maybe centered, within ±10% of the center 7 of the glass ribbon 20.

Lastly, as far as the characteristics of the interlayer, the complianceof the interlayer material 40 plays a role in forming a roll 10 withstraight side walls by compensating for thickness variation in the glassribbon 20. The effects of thickness variation will be described withreference to FIG. 6. In this figure, ignoring beads 30 for the moment,the glass ribbon is shown with a thickness 27 on a left-hand edge and asecond, greater, thickness 29 on the right-hand edge. If the interlayer40 were not compliant, but rigid, the greater thickness 29 would causethe glass ribbon 20 to tilt upwards from left to right (as when viewingthe top portion of the roll 10 as shown in FIG. 6). In so tilting, layer23 would then tend to push the next layer 23 in the direction of arrow 5causing the side wall of the roll 10 to shift rightward. The effects ofthe thickness difference would build on one another as it is likely thatthe same differences in thickness 27, 29 would be repeated as the ribbon20 is formed. However, by choosing a compliant interlayer material 40,the interlayer 40 compensates for the difference in thicknesses 27, 29.More specifically, the interlayer 40 would compress more when adjacentto the portion of the glass ribbon 20 having a greater thickness 29, andcompress less when adjacent to the portion of the glass ribbon 20 havingthe smaller thickness 27. That is, as shown in FIG. 6, under rollcompression, the interlayer 40 would assume a smaller thickness 49 theright-hand side, and a greater thickness 47 on the left-hand side,thereby allowing the layer 23 to assume an approximately horizontalorientation despite its difference in thicknesses 27, 29. In this case,thickness 49 is still sufficient to maintain a suitable gap 34 betweenthe beads 30. A suitable stiffness for the interlayer material 40 wasfound to be less than or equal to about 28.14 N/mm, or less than orequal to about 27.12 N/mm, or less than or equal to about 26.1 N/mm,wherein the lower bound for all ranges was greater than zero. In orderto achieve the above-noted stiffness, the interlayer 40 may be formedfrom, for example, a polyethylene foam (either open or closed cell), acorrugated paper material, or a sheet of soft polyvinyl material havingan embossed or textured surface.

The rolling conditions also play a part in forming a roll with straightside walls. Some pertinent rolling conditions are web tension andpressure between the layers in the roll. Surprisingly, the inventorsfound that using a low web tension and a low pressure between the layersproduced straighter side walls in the roll—i.e., where “low” was lowerthan typically expected. More particularly, a web tension of greaterthan 0 pounds per linear inch (0 kg/cm), but 0.25 pounds per linear inch(0.45 kg/cm) or less, produced straight side walls on the roll.Additionally, a pressure between the layers in the roll of 10 pounds persquare inch (0.703 kg/square cm) or less, but greater than 0 pounds persquare inch (0 kg/square cm), produced straight side walls on the roll.Another pressure between the layers in the roll of 7 pounds per squareinch (0.492 kg/square cm) or less, but greater than 0 pounds per squareinch (0 kg/square cm), also produced straight side walls on the roll.Further, the above-noted coefficients of friction between the interlayerand glass ribbon facilitated using the above-noted unusually low webtension and pressure between the layers in the roll. The web tension andpressure ranges may be used with any of the configurations of glassribbon 20 and interlayer material 40 described herein to produce theabove-noted minimal lateral offsets 9, even when the roll includes up toabout 150 layers or more of glass ribbon 20.

It should be emphasized that the above-described embodiments of thepresent invention, particularly any “preferred” embodiments, are merelypossible examples of implementations, merely set forth for a clearunderstanding of various principles of the invention. Many variationsand modifications may be made to the above-described embodiments of theinvention without departing substantially from the spirit and variousprinciples of the invention. All such modifications and variations areintended to be included herein within the scope of this disclosure andthe present invention and protected by the following claims.

For example, although the core is shown without flanges on its ends,flanges could be present. Further, the flanges could be permanentlyattached to the core, or could be removable.

Additionally, although three layers of interlayer and three layers ofglass ribbon are shown as being wound on a roll, any suitable number oflayers of either may be present.

Further, although a layer of glass ribbon is shown as being theoutermost layer of the roll, it need not be. That is, the interlayer maybe wound one or more times around the outer-most layer of glass ribbonin order to protect that layer. Similarly, although an interlayer isshown as being the inner-most layer of the roll, it need not be; theinner-most layer of glass ribbon could be the inner-most layer of theroll. Nonetheless, it is preferable to have an interlayer as theinner-most layer of the roll in order to protect the inner-most layer ofglass ribbon.

Still further, although the center 7 of the glass ribbon 20 is shown asbeing aligned with the center 14 of the core 12, such need not be thecase.

What is claimed is:
 1. A roll of glass ribbon, comprising: a glassribbon; an interlayer wound together with the glass ribbon, wherein theglass ribbon has a thickness of 0.3 mm or less, wherein the staticcoefficient of friction between the interlayer and the glass ribbon isgreater than or equal to 3.0 (as measured with a vertical force of 0.5N).
 2. The roll according to claim 1, wherein the stiffness of theinterlayer is less than or equal to 28.14 N/mm.
 3. The roll according toclaim 1, wherein the pressure between successive layers of glass ribbonis less than or equal to 10 pounds per square inch (0.703 kg/square cm).4. The roll according to claim 1, wherein the interlayer and glassribbon are wound so that a lateral offset between an inner-most layer ofthe glass ribbon and an outer-most layer of glass ribbon is less than orequal to 1.6 mm.
 5. The roll according to claim 1, wherein theinterlayer comprises a first portion and a second portion disposed at adistance from one another and having a width, wherein the width iscentered within ±10% of the center of the glass ribbon, wherein theglass ribbon has an outboard end portion, and further wherein there isno interlayer disposed on the outboard end portion.
 6. The rollaccording to claim 1, wherein the interlayer has a first width, theglass ribbon has a second width and an outboard end portion, wherein thefirst width is less than the second width, and further wherein there isno interlayer disposed on the outboard end portion.
 7. The rollaccording to claim 1, wherein the glass ribbon comprises a bead on oneof its edges and wherein the interlayer has a thickness when compressedat a roll-winding pressure up to 70 kPa (10 psi), the bead has athickness, and the interlayer thickness is greater than a differencebetween the bead thickness and the ribbon thickness.
 8. A method ofwinding a glass ribbon, comprising: winding an interlayer together witha glass ribbon, wherein the glass ribbon has a thickness of 0.3 mm orless, wherein the static coefficient of friction between the interlayerand the glass ribbon is greater than or equal to 3.0 (as measured with avertical force of 0.5 N).
 9. The method according to claim 8, whereinthe stiffness of the interlayer is less than or equal to 28.14 N/mm. 10.The method according to claim 8, wherein the winding is performed sothat a resulting pressure between successive layers of glass ribbon isgreater than zero pounds per square inch (0 kg/square cm) and is lessthan or equal to 10 pounds per square inch (0.703 kg/square cm).
 11. Themethod according to claim 8, wherein the winding is performed with a webtension of greater than zero pounds per linear inch (0 kg/cm) and ofless than or equal to 0.25 pounds per linear inch (0.45 kg/cm) on theglass ribbon.
 12. The method according to claim 8, wherein the windingis performed so that the glass ribbon is disposed in an inner-most layerand an outer-most layer, wherein a lateral offset between the inner-mostlayer and the outer-most layer is less than or equal to 1.6 mm.
 13. Themethod according to claim 8, wherein the interlayer comprises a firstportion and a second portion disposed at a distance from one another andhaving a width, wherein the width is centered within ±10% of the centerof the glass ribbon, wherein the glass ribbon has an outboard endportion, and further wherein there is no interlayer disposed on theoutboard end portion.
 14. The method according to claim 8, wherein theinterlayer has a first width, the glass ribbon has a second width and anoutboard end portion, wherein the first width is less than the secondwidth, and further wherein there is no interlayer disposed on theoutboard end portion.
 15. The method according to claim 8, wherein theglass ribbon comprises a bead on one of its edges and wherein theinterlayer has a thickness when compressed at a roll-winding pressure upto 70 kPa (10 psi), the bead has a thickness, and the interlayerthickness is greater than a difference between the bead thickness andthe ribbon thickness.
 16. A roll of material comprising: interleavingmaterial wound together with glass ribbon, wherein a pressure betweenlayers in the roll is ≦10 pounds per square inch (0.703 kg/square cm),and is greater than 0 pounds per square inch (0 kg/square cm).
 17. Theroll of material of claim 16, wherein the interleaving material isthickness compliant.
 18. The roll of material of claim 17, wherein theinterleaving material is polyethylene foam.
 19. The roll of material ofclaim 16, wherein the inter-layer roll pressure is approximatelyconstant throughout the roll.
 20. The roll of material of claim 16,wherein the glass ribbon has a thickness ≦0.3 mm.